Results of Single-Session Bilateral Tibial Plateau Leveling Osteotomies as a Treatment for Bilaterally Ruptured Cranial Cruciate Ligaments in Dogs: 25 Cases (2000–2001)

Introduction

Cranial cruciate ligament (CrCL) rupture is one of the most common orthopedic injuries in dogs. Unilateral hind-limb lameness is the most common presenting complaint for CrCL rupture, and 21% to 60% of these dogs may ultimately rupture the contralateral CrCL within an average of 14 months of the first injury.^1–3 A small number of patients, however, may present with bilateral hind-limb difficulties associated with CrCL disease. Bilateral injuries have been reported to occur in as many as 31% of dogs with CrCL disease.⁴ These dogs may present with hind-limb stiffness rather than the typical hind-limb lameness.⁵ Young, large-breed dogs appear to be at greater risk for such a presentation, and an initial incorrect diagnosis of hip dysplasia may be made.¹⁵ In the author’s experience, staged surgeries have been most commonly performed in these cases because of the perception of a greater risk for complications if both stifles are operated in a single session. Staged procedures, however, require overall longer durations of anesthesia, doubled periods of postoperative recovery, and greater owner expense than would be incurred with definitive single-session repairs. While many surgical procedures have been reported for stabilization of the unilateral CrCL-deficient stifle, the utility of these procedures for single-session bilateral treatment is not well described. To the author’s knowledge, the results of single-session surgical treatment of bilateral CrCL disease have not been reported.

All traditional surgical techniques attempt to restore stifle stability by mimicking the passive restraint provided by an intact CrCL. These procedures have been classified as extracapsular or intracapsular stabilization. Regardless of the technique employed, it is the development of secondary periarticular fibrosis that provides long-term stifle stability. The tibial plateau leveling osteotomy (TPLO) is a unique technique that does not restore passive stifle stability but instead functionally stabilizes the stifle during weight bearing by eliminating cranial tibial thrust (CTT). Cranial tibial thrust is the cranially directed force generated by tibial compression during weight bearing.⁶ Cranial tibial subluxation occurs when this force is not opposed by an intact CrCl.⁶⁷ Good to excellent clinical results have described using the TPLO for treatment of unilateral CrCL rupture, and biomechanical studies have confirmed its utility in reducing or eliminating CTT.^8–10 Since TPLO does not rely on implants or autogenous tissue to directly oppose CTT or periarticular fibrosis development to maintain stifle stability, it might be well applied in cases of bilateral CrCL injury where single-session repair is desirable.

The purposes of this study were to describe the clinical features of bilateral CrCL rupture and to present the results of treatment using single-session bilateral TPLO surgeries in 25 dogs.

Materials and Methods

The medical records of all dogs that underwent single-session bilateral TPLOs between August 2000 and December 2001 at MedVet Associates, Inc., were reviewed. Dogs were included in the study if they had been returned for at least one follow-up visit at ≥6 weeks following surgery and if a completed owner questionnaire was returned.

Information gathered from the medical records included patient signalment, body weight, lameness history, initial physical examination findings, intra- and perioperative complications, and physical examination findings at follow-ups. Clinical function was determined by the degree of lameness/stiffness observed [Table 1]. Physical examination findings included degree of patient lameness, lateralization of lameness, and distribution of partial and full CrCL ruptures. Partially ruptured CrCLs were defined as stifles that only had a cranial drawer in flexion, a slight cranial drawer in flexion and extension, or no cranial drawer sign associated with stifle periarticular fibrosis, joint effusion, and pain elicited on stifle manipulation. A stifle with a cranial drawer sign in both extension and flexion was defined as having a fully ruptured CrCL.

Tibial plateau osteotomies were performed on both stifles of each dog sequentially. The TPLOs were performed by the author according to the technique described by Slocum.⁸¹¹ Patients were discharged 24 to 48 hours following surgery. Owners were instructed to maintain strict confinement of their dog to a cage or small room and to limit exercise to short leash walks for elimination purposes only until the first follow-up visit. All dogs were discharged with a sling to assist with ambulation. The owners were advised to use it for the first 2 weeks postoperatively, and then as needed.

Early postoperative clinical function information was gathered from all dogs during the first follow-up physical examination performed by the author at 6 to 10 weeks following surgery, and function was classified as previously described. Radiographs were taken at this time to evaluate osteotomy healing. Following completion of the examination, all owners were instructed to follow a 6-week rehabilitation plan and to present their dogs for final recheck at the end of the rehabilitation period. Rehabilitation consisted of 2 weeks of walks on a short leash, followed by 2 weeks of walks on a 10- to 15-foot long leash, and then 2 weeks of off-leash activities in an enclosed area under supervision. Additional long-term function information was gathered from a questionnaire mailed to owners. The questionnaire was derived from one used by Olmstead to evaluate patient function following total hip replacement.¹² In addition, owners were also asked to rate overall function once their dogs had resumed normal activity, using the same criteria previously described for evaluation of clinical function [Table 2].

Results

Twenty-six dogs met the selection criteria and were evaluated for this study. One German shepherd dog was ultimately excluded because it had semitendinosus fibrotic myopathy that progressed through the postoperative period, making interpretation of functional results difficult. The mean age at presentation was 4.9 years (range, 2 to 11 years). There were 17 spayed females, one intact female, and seven castrated males. Breeds included mixed (n=8); Labrador retriever, golden retriever, rottweiler (n=4 each); standard poodle (n=2); and bullmastiff, German shepherd dog, and West Highland white terrier (n=1 each). Mean body weight was 36.1 kg (range, 8.6 to 57.2 kg).

The primary presenting complaint for every dog was hind-limb lameness or stiffness. Seven of 25 dogs were presented for unilateral lameness, while 18 were presented for bilateral hind-limb lameness that was described as a stiffness or difficulty walking rather than obvious limping. All of the dogs with bilateral hind-limb lameness had a history of unilateral lameness that had progressed, either acutely or chronically, to difficulties with both legs. In 11 of the 18 dogs, the unilateral lameness preceded bilateral lameness by >3 months. One dog had a lateral retinacular imbricating suture placed previously in one stifle for treatment of a torn CrCL 4 months prior to presentation.

All of the dogs that presented for bilateral lameness or stiffness had one hind limb that was more affected than the other. In these cases, the more affected limb was the one most recently injured. Of 25 dogs, five had bilateral complete CrCL ruptures, six had bilateral partial ruptures, and 13 had one partially and one fully ruptured CrCL. The remaining dog had a previously operated stifle with recurrent instability and pain and a partially ruptured contralateral CrCL. Function was rated as fair in 19 dogs and poor in the remaining six dogs.

Of the 50 operated stifles, one had a combination closing wedge ostectomy and TPLO (CWO/TPLO); eight had prophylactic tibial tuberosity wire tension bands placed during the TPLO; and the remaining 41 had routine TPLOs. All stifles had arthrotomies made just caudal to the medial collateral ligament or within the caudal one-third of the ligament. Partial medial meniscectomies were performed in seven stifles and medial meniscal releases were performed in 43 stifles. All patients had morphine^a epidurals (0.1 mg/kg body weight) preoperatively, and intramuscular morphine (0.5 mg/kg body weight) was used as needed for 24 to 48 hours postoperatively. All patients were discharged with a 7-day supply of either carprofen^b (2.2 mg/kg body weight, per os [PO], bid) or etodolac^c (10 to 15 mg/kg body weight, PO, sid). No intraoperative complications were encountered.

Postoperative complications occurred in five stifles of five dogs. Each dog had developed an incisional infection of one operated stifle. Treatment with cephalexin (22 mg/kg body weight, PO, tid for 14 days) and Elizabethan collars resulted in complete resolution in each patient.

Twenty-one dogs were seen for suture removal at 10 to 14 days postoperatively. No dog required any assistance while walking, and all owners had discontinued sling use by this time. No additional pain medication had been administered by the owners beyond what had been prescribed.

The mean time to the first follow-up visit was 6.9 weeks (range, 6 to 10 weeks). All radiographs revealed progressing but incomplete osteotomy healing. The amount of healing, however, was deemed adequate for beginning rehabilitation in all cases. Clinical function was rated as excellent in six dogs, good in 13 dogs, and fair in six dogs. Ten dogs were presented for the 12-week follow-up. All of the owners described that their dogs had tolerated rehabilitation activities well with no problems encountered. Clinical function was rated as excellent in nine dogs and good in one dog.

Mean time between surgery and completion of the owner questionnaires was 14.3 months (range, 8 to 22.5 months). Postoperative function during specific activities improved in 18 dogs by two or more grades, with a mean increase of 2.1 functional grades among the 25 dogs [Tables 3, 4]. Overall function was rated as excellent in 15 dogs, good in eight dogs, and fair in two dogs.

Discussion

The prevalence of bilateral CrCL ruptures has been reported to be 31% in dogs.⁴ During the time of this study, bilateral ruptures were diagnosed in 10% of dogs evaluated at the author’s hospital for CrCL injury. More than half of the dogs in this study were ≤4 years of age, and body weight was >30 kg for 20 of the 25 dogs. These findings are similar to previous reports, which reported that 21% to 31% of young, large-breed dogs had bilateral CrCL tears at initial presentation.¹⁵ All but one of the dogs in this study were neutered, and 18 of the 25 dogs were female. Both females and neutered dogs of both sexes have been reported to be at an increased risk for CrCL rupture.¹³¹³ Risk factors, however, cannot be presumed from data in this study, because comparison to a hospital population control group was not feasible.

Cranial cruciate ligament rupture in the dog is most often spontaneous and can be caused by primary degeneration of the ligament.¹⁴ Ligamentous degeneration likely accounts for the 21% to 60% of dogs with unilateral CrCL rupture that ultimately ruptures the contralateral CrCL.^1–3 The dogs in this study are a part of this group that have both CrCLs ruptured at initial presentation. The typical history for these dogs included a chronic (58% of dogs were lame >3 months), unilateral hind-limb lameness that acutely progressed to bilateral lameness or stiffness without known trauma. The duration and progression of the lameness are consistent with gradual tearing of one ligament followed by a spontaneous, acute, full or partial tear of the contralateral CrCL.⁵¹⁴ Hind-limb stiffness rather than overt lameness was the most common presenting complaint. Owners typically described that their dogs had difficulty with both hind limbs, walked with a stiff gait, and had problems performing many normal activities. This atypical presentation for CrCL injury led to approximately one-third of these dogs being referred for suspected neurological disease or hip joint problems.

Only 14% of the stifles operated in this study were diagnosed with a torn medial meniscus. This finding is below the 20% meniscal injury described in stifles with partially torn CrCLs and the 53% associated with complete ruptures.¹⁴¹⁵ It is possible that the small caudal medial arthrotomy used with the TPLO procedure may cause some tears of the lateral portion of the medial meniscus to go unobserved. However, if significant tears were not diagnosed, then persistent lameness and a poor functional result would be expected.³¹⁶ Since such findings were not noted, either meniscal injury was uncommon in these cases or meniscal release provided resolution of clinical signs associated with an unseen meniscal tear, similar to that of a meniscectomy.

To the author’s knowledge, there are no reports specifically addressing treatment of bilaterally ruptured CrCLs. Single-session bilateral stifle surgery offers the advantages of only requiring one period of anesthesia and recovery, decreased cost to owners, and an overall quicker recovery than staggered procedures. Dogs are also not required to walk on a subluxating stifle while the operated leg heals. However, since the majority of these patients tend to be large-breed dogs,¹⁵ operating on both stifles in a single session would be expected to greatly stress implants or tissues used for stabilization and increase the likelihood of recurrent instability and complications. While not previously evaluated for single-session bilateral repair, extracapsular and intracapsular techniques would be expected to be of more limited value in these cases, because the materials utilized never achieve the maximal strength of a normal CrCL, and they depend on the development of periarticular fibrosis for stifle stability. The TPLO procedure does not rely on implants, autogenous tissues, or periarticular fibrosis to passively constrain cranial tibial subluxation. Immediate and long-term elimination of cranial tibial subluxation during weight bearing is expected following completion of the procedure.^6–10 These attributes would be expected to make the TPLO uniquely well suited for patients that require early and continuous functional stifle stability.

Intra- and postoperative complications for extracapsular techniques are variable, with reported rates ranging as high as 21% to 41% depending on the technique(s) employed.^17–19 While not described, similar, if not higher, rates would be expected for single-session extracapsular repair of bilateral CrCL rupture. Single-session bilateral TPLOs were not associated with any severe intra- or postoperative complications. Postoperative discomfort did not appear to be a problem, as all of the dogs in this study were able to walk with minimal assistance within 12 hours of surgery. Of the 21 dogs seen at 10 to 14 days postoperatively for suture removal, none required any assistance while walking or had been given any additional pain medication by their owners beyond what was prescribed. Observer assessment of pain is subjective; however, the rapid willingness of these patients to walk with only minimal sling support shortly after surgery suggests that postoperative pain is not a contraindication for single-session bilateral stifle surgery.

Tibial tuberosity avulsion fractures have been described as a potential complication of TPLOs.¹¹²⁰ Tuberosities that are cut thin during the osteotomy or large rotations of the tibial plateau that isolate the tibial tuberosity, may predispose to avulsion.¹¹ Prophylactic tibial tuberosity wire tension bands in cases of thin cuts and a CWO/TPLO in patients with plateau angles >34° have been suggested as means to help prevent avulsion fractures.¹¹ Tension bands were used in eight stifles in this study. They were utilized in cases where the author had concerns regarding the tuberosity thickness postosteotomy. A CWO/TPLO was used in one stifle in this report with a tibial plateau angle of 45°. Five other stifles, however, had angles >34° and did not have the combined procedure done. None of the tibias, with or without tension bands or CWO/TPLO, developed avulsion fractures in this study. However, since neither the minimum tuberosity thickness requirement nor the maximum allowable tibial osteotomy rotation for preventing avulsion has yet to be reported, the necessity for or effectiveness of prophylactic tension bands or a CWO/TPLO is not known. Whether they actually helped prevent avulsion in these cases cannot be determined.

Objective measurement of limb function necessitates kinematic gait analysis that was not available for this study. However, veterinarian and owner-based assessments can offer relevant insight into functional outcomes.²¹²² Good or excellent function was recorded in 19 of 25 dogs as early as 6 weeks postoperatively and in 10 of 10 dogs by 12 weeks postoperatively. These findings are similar to previously reported short-term results for unilateral TPLOs and extracapsular repairs.⁸²³

According to owners, climbing stairs appeared to be the most difficult activity for dogs with bilateral CrCL rupture, followed closely by running and play activity. None of the dogs were able to perform these activities normally or near normally preoperatively compared to the approximately 78% of dogs that had normal to near-normal performance postoperatively. Owner evaluation results revealed that 92% of dogs were rated as having good or excellent overall function at an average of 14.3 months following surgery.

Conclusion

Bilateral CrCL rupture is an uncommon presentation for CrCL injury. Historical and physical examination features differ from unilateral injury. Bilateral CrCL rupture should be included as a differential in dogs with hind-limb stiffness and activity difficulties more typical of coxofemoral joint disease. Single-session bilateral TPLOs were successful in providing good to excellent results in the majority of patients as early as 6 weeks postoperatively. Perioperative morbidity was low. All dogs were able to walk with minimal assistance shortly after surgery, and postoperative complications were uncommon. When encountered, complications were minor and resolved completely with treatment. This study demonstrates that definitive surgical treatment of bilaterally ruptured CrCLs with single-session bilateral TPLOs is a safe and effective alternative to staged procedures.